Change random seeds to 64bit and drop re-crcing

I had some trouble with random build failures in a large LTO project
and it turned out to be random seed collisions in a highly parallel build
(thanks to Honza for suggesting that)

There were multiple problems:
- The way to generate the random seed is not very random (milliseconds time plus pid)
and prone to collisions on highly parallel builds
- It's only 32bit
- Several users take the existing ascii seed and re-CRC32 it again, which
doesn't exactly improve it.

This patch changes that to:
- Always use 64bit seeds as numbers (no re-crcing)
- Change all users to use HOST_WIDE_INT
- When the user specifies a random seed it's still crc32ed, but only in
this case.

Passes bootstrap + testsuite on x86_64-linux.

gcc/cp:

2011-09-26   Andi Kleen <ak@linux.intel.com>

	* repo.c (finish_repo): Use HOST_WIDE_INT_PRINT_HEX_PURE.

gcc/:

2011-09-26   Andi Kleen <ak@linux.intel.com>

	* hwint.h (HOST_WIDE_INT_PRINT_HEX_PURE): Add.
	* lto-streamer.c (lto_get_section_name): Remove crc32_string.
 	Handle numerical random seed.
	* lto-streamer.h (lto_file_decl_data): Change id to unsigned HOST_WIDE_INT.
	* toplev.c (random_seed): Add.
	(init_random_seed): Change for numerical random seed.
	(get_random_seed): Return as HOST_WIDE_INT.
	(set_random_seed): Crc32 existing string.
	* toplev.h (get_random_seed): Change to numercal return.
	* tree.c (get_file_function_name): Remove CRC. Handle numerical random seed.

gcc/lto/:

2011-09-26   Andi Kleen <ak@linux.intel.com>

	* lto.c (lto_resolution_read): Remove id dumping.
	(lto_section_with_id): Turn id HOST_WIDE_ID.
	(create_subid_section_table): Dito.

git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@179347 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 17 insertions, 10 deletions

diff --git a/gcc/toplev.c b/gcc/toplev.c
index 3688c093a3f..78583fc52a6 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -141,6 +141,9 @@ static const char *flag_random_seed;
    user has specified a particular random seed.  */
 unsigned local_tick;
 
+/* Random number for this compilation */
+HOST_WIDE_INT random_seed;
+
 /* -f flags.  */
 
 /* Generate code for GNU or NeXT Objective-C runtime environment.  */
@@ -251,7 +254,7 @@ announce_function (tree decl)
     }
 }
 
-/* Initialize local_tick with the time of day, or -1 if
+/* Initialize local_tick with a random number or -1 if
    flag_random_seed is set.  */
 
 static void
@@ -286,24 +289,28 @@ init_local_tick (void)
 static void
 init_random_seed (void)
 {
-  unsigned HOST_WIDE_INT value;
-  static char random_seed[HOST_BITS_PER_WIDE_INT / 4 + 3];
-
-  value = local_tick ^ getpid ();
+  if (flag_random_seed)
+    {
+      char *endp;
 
-  sprintf (random_seed, HOST_WIDE_INT_PRINT_HEX, value);
-  flag_random_seed = random_seed;
+      /* When the driver passed in a hex number don't crc it again */
+      random_seed = strtoul (flag_random_seed, &endp, 0);
+      if (!(endp > flag_random_seed && *endp == 0))
+        random_seed = crc32_string (0, flag_random_seed);
+    }
+  else if (!random_seed)
+    random_seed = local_tick ^ getpid ();  /* Old racey fallback method */
 }
 
-/* Obtain the random_seed string.  Unless NOINIT, initialize it if
+/* Obtain the random_seed.  Unless NOINIT, initialize it if
    it's not provided in the command line.  */
 
-const char *
+HOST_WIDE_INT
 get_random_seed (bool noinit)
 {
   if (!flag_random_seed && !noinit)
     init_random_seed ();
-  return flag_random_seed;
+  return random_seed;
 }
 
 /* Modify the random_seed string to VAL.  Return its previous